Old School

You can but they are going to top out at a total height of around 3. Try pinching/topping/pruning/FIM to the growth top and give the side shoots a chance to catch up to the main stalk (about a week if in hydro) and then you will double or triple your final yield

Here is the deal we are talking light cycle. 18/6 is the amout of time the light is on 18 on 6 off this is early in the development of weed plants known as vegitative state. after about 4-6 weeks you put the plant into flowering in order to do that you need to put the plants on a 12 hour photoperiod that is 12/12 and that is 12 hours on 12 hours off hope this helped you out allittle.